diff options
Diffstat (limited to 'src/lib/gpio.c')
| -rw-r--r-- | src/lib/gpio.c | 49 |
1 files changed, 47 insertions, 2 deletions
diff --git a/src/lib/gpio.c b/src/lib/gpio.c index 5147cfebac..2e345956f8 100644 --- a/src/lib/gpio.c +++ b/src/lib/gpio.c @@ -35,7 +35,7 @@ int gpio_base2_value(gpio_t gpio[], int num_gpio) return result; } -int gpio_base3_value(gpio_t gpio[], int num_gpio) +int _gpio_base3_value(gpio_t gpio[], int num_gpio, int binary_first) { /* * GPIOs which are tied to stronger external pull up or pull down @@ -50,6 +50,8 @@ int gpio_base3_value(gpio_t gpio[], int num_gpio) int temp; int index; int result = 0; + int has_z = 0; + int binary_below = 0; char value[32]; assert(num_gpio <= 32); @@ -85,8 +87,51 @@ int gpio_base3_value(gpio_t gpio[], int num_gpio) temp |= ((value[index] ^ temp) << 1); printk(BIOS_DEBUG, "%c ", tristate_char[temp]); result = (result * 3) + temp; + + /* + * For binary_first we keep track of the normal ternary result + * and whether we found any pin that was a Z. We also determine + * the amount of numbers that can be represented with only + * binary digits (no Z) whose value in the normal ternary system + * is lower than the one we are parsing. Counting from the left, + * we add 2^i for any '1' digit to account for the binary + * numbers whose values would be below it if all following + * digits we parsed would be '0'. As soon as we find a '2' digit + * we can total the remaining binary numbers below as 2^(i+1) + * because we know that all binary representations counting only + * this and following digits must have values below our number + * (since 1xxx is always smaller than 2xxx). + * + * Example: 1 0 2 1 (counting from the left / most significant) + * '1' at 3^3: Add 2^3 = 8 to account for binaries 0000-0111 + * '0' at 3^2: Ignore (not all binaries 1000-1100 are below us) + * '2' at 3^1: Add 2^(1+1) = 4 to account for binaries 1000-1011 + * Stop adding for lower digits (3^0), all already accounted + * now. We know that there can be no binary numbers 1020-102X. + */ + if (binary_first && !has_z) { + switch(temp) { + case 0: /* Ignore '0' digits. */ + break; + case 1: /* Account for binaries 0 to 2^index - 1. */ + binary_below += 1 << index; + break; + case 2: /* Account for binaries 0 to 2^(index+1) - 1. */ + binary_below += 1 << (index + 1); + has_z = 1; + } + } + } + + if (binary_first) { + if (has_z) + result = result + (1 << num_gpio) - binary_below; + else /* binary_below is normal binary system value if !has_z. */ + result = binary_below; } - printk(BIOS_DEBUG, "= %d\n", result); + + printk(BIOS_DEBUG, "= %d (%s base3 number system)\n", result, + binary_first ? "binary_first" : "standard"); /* Disable pull up / pull down to conserve power */ for (index = 0; index < num_gpio; ++index) |